<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    
    <form >
        <div>
            用户名 : <input class='username'/>
        </div>
        <div>
            密码 : <input class='password'/>
        </div>
        <button type="button" class="btn" disabled>提交</button>
    </form>
    <script src="https://apps.bdimg.com/libs/jquery/2.1.4/jquery.min.js"></script>
    <script src="./form.js"></script>
</body>
</html>